Sean Christopherson <seanjc@xxxxxxxxxx> writes:
> Drop the @selector from the kernel code, data, and TSS builders and
> instead hardcode the respective selector in the helper. Accepting a
> selector but not a base makes the selector useless, e.g. the data helper
> can't create per-vCPU for FS or GS, and so loading GS with KERNEL_DS is
> the only logical choice.
>
> And for code and TSS, there is no known reason to ever want multiple
> segments, e.g. there are zero plans to support 32-bit kernel code (and
> again, that would require more than just the selector).
>
> If KVM selftests ever do add support for per-vCPU segments, it'd arguably
> be more readable to add a dedicated helper for building/setting the
> per-vCPU segment, and move the common data segment code to an inner
> helper.
>
> Lastly, hardcoding the selector reduces the probability of setting the
> wrong selector in the vCPU versus what was created by the VM in the GDT.
>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> ---
> .../selftests/kvm/lib/x86_64/processor.c | 29 +++++++++----------
> 1 file changed, 14 insertions(+), 15 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c
> index dab719ee7734..6abd50d6e59d 100644
> --- a/tools/testing/selftests/kvm/lib/x86_64/processor.c
> +++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c
> @@ -438,10 +438,10 @@ static void kvm_seg_fill_gdt_64bit(struct kvm_vm *vm, struct kvm_segment *segp)
> desc->base3 = segp->base >> 32;
> }
>
> -static void kvm_seg_set_kernel_code_64bit(uint16_t selector, struct kvm_segment *segp)
> +static void kvm_seg_set_kernel_code_64bit(struct kvm_segment *segp)
> {
> memset(segp, 0, sizeof(*segp));
> - segp->selector = selector;
> + segp->selector = KERNEL_CS;
> segp->limit = 0xFFFFFFFFu;
> segp->s = 0x1; /* kTypeCodeData */
> segp->type = 0x08 | 0x01 | 0x02; /* kFlagCode | kFlagCodeAccessed
> @@ -452,10 +452,10 @@ static void kvm_seg_set_kernel_code_64bit(uint16_t selector, struct kvm_segment
> segp->present = 1;
> }
>
> -static void kvm_seg_set_kernel_data_64bit(uint16_t selector, struct kvm_segment *segp)
> +static void kvm_seg_set_kernel_data_64bit(struct kvm_segment *segp)
> {
> memset(segp, 0, sizeof(*segp));
> - segp->selector = selector;
> + segp->selector = KERNEL_DS;
> segp->limit = 0xFFFFFFFFu;
> segp->s = 0x1; /* kTypeCodeData */
> segp->type = 0x00 | 0x01 | 0x02; /* kFlagData | kFlagDataAccessed
> @@ -480,13 +480,12 @@ vm_paddr_t addr_arch_gva2gpa(struct kvm_vm *vm, vm_vaddr_t gva)
> return vm_untag_gpa(vm, PTE_GET_PA(*pte)) | (gva & ~HUGEPAGE_MASK(level));
> }
>
> -static void kvm_seg_set_tss_64bit(vm_vaddr_t base, struct kvm_segment *segp,
> - int selector)
> +static void kvm_seg_set_tss_64bit(vm_vaddr_t base, struct kvm_segment *segp)
> {
> memset(segp, 0, sizeof(*segp));
> segp->base = base;
> segp->limit = 0x67;
> - segp->selector = selector;
> + segp->selector = KERNEL_TSS;
> segp->type = 0xb;
> segp->present = 1;
> }
> @@ -510,11 +509,11 @@ static void vcpu_init_sregs(struct kvm_vm *vm, struct kvm_vcpu *vcpu)
> sregs.efer |= (EFER_LME | EFER_LMA | EFER_NX);
>
> kvm_seg_set_unusable(&sregs.ldt);
> - kvm_seg_set_kernel_code_64bit(KERNEL_CS, &sregs.cs);
> - kvm_seg_set_kernel_data_64bit(KERNEL_DS, &sregs.ds);
> - kvm_seg_set_kernel_data_64bit(KERNEL_DS, &sregs.es);
> - kvm_seg_set_kernel_data_64bit(KERNEL_DS, &sregs.gs);
> - kvm_seg_set_tss_64bit(vm->arch.tss, &sregs.tr, KERNEL_TSS);
> + kvm_seg_set_kernel_code_64bit(&sregs.cs);
> + kvm_seg_set_kernel_data_64bit(&sregs.ds);
> + kvm_seg_set_kernel_data_64bit(&sregs.es);
> + kvm_seg_set_kernel_data_64bit(&sregs.gs);
> + kvm_seg_set_tss_64bit(vm->arch.tss, &sregs.tr);
>
> sregs.cr3 = vm->pgd;
> vcpu_sregs_set(vcpu, &sregs);
> @@ -588,13 +587,13 @@ static void vm_init_descriptor_tables(struct kvm_vm *vm)
>
> *(vm_vaddr_t *)addr_gva2hva(vm, (vm_vaddr_t)(&exception_handlers)) = vm->handlers;
>
> - kvm_seg_set_kernel_code_64bit(KERNEL_CS, &seg);
> + kvm_seg_set_kernel_code_64bit(&seg);
> kvm_seg_fill_gdt_64bit(vm, &seg);
>
> - kvm_seg_set_kernel_data_64bit(KERNEL_DS, &seg);
> + kvm_seg_set_kernel_data_64bit(&seg);
> kvm_seg_fill_gdt_64bit(vm, &seg);
>
> - kvm_seg_set_tss_64bit(vm->arch.tss, &seg, KERNEL_TSS);
> + kvm_seg_set_tss_64bit(vm->arch.tss, &seg);
> kvm_seg_fill_gdt_64bit(vm, &seg);
> }
>
> --
> 2.44.0.291.gc1ea87d7ee-goog
Reviewed-by: Ackerley Tng <ackerleytng@xxxxxxxxxx>
